VisualGGPK
This is viewer for GGPK files. It shows internal structure of files and folders in tree view and allows:

viewing data in the internal Viewer: pictues, text files, or special table viewer for .dat files

exporting fiels or directories from context menu

replacing content of files with other data

delete files and directories and save clipped GGPK file. For example, clipped GGPK filewith only Data\ folder
occupies only 15 Mb of space and loads in 1 second in VisualGGPK instead of 20-40 seconds.
Of course, such file couldn't be used for game.

opening file in the external application on double mouse click (.dat files open as CSV file)